[Bug] workspaces list result is not json

• I’d be willing to implement a fix

Describe the bug

run yarn workspaces list -v --json in a workspace, but the received output is not a valid JSON string

To Reproduce

---

Playground

const {promises: {writeFile, mkdir}} = require(`fs`);

await mkdir('packages');

await mkdir('packages/a');

await writeFile('packages/a/package.json', JSON.stringify({
name: 'a',
}));

await mkdir('packages/b');

await writeFile('packages/b/package.json', JSON.stringify({
name: 'b'
}));


await packageJsonAndInstall({
workspaces: {
packages: [
  "packages/*"
]
},
});

const output = await yarn(`workspaces`, `list`, `-v`, `--json`);

expect(output).not.toContain(`yarn`);
expect(output).toContain(`yarn`);


expect(() => JSON.parse(output)).not.toThrow();

Output:

Error: expect(received).toContain(expected) // indexOf

Expected substring: "yarn"
Received string:    "{\"location\":\".\",\"name\":null,\"workspaceDependencies\":[],\"mismatchedWorkspaceDependencies\":[]}
{\"location\":\"packages/a\",\"name\":\"a\",\"workspaceDependencies\":[],\"mismatchedWorkspaceDependencies\":[]}
{\"location\":\"packages/b\",\"name\":\"b\",\"workspaceDependencies\":[],\"mismatchedWorkspaceDependencies\":[]}
"
at module.exports (evalmachine.<anonymous>:31:16)
at process._tickCallback (internal/process/next_tick.js:68:7)

---

Screenshots

Environment if relevant (please complete the following information):

• OS: OSX
• Node version 12
• Yarn version 2.4.0

Additional context

yarn 1 outputs a object text:

{
  "a": {
    location: "packages/a",
    workspaceDependencies: [],
    mismatchedWorkspaceDependencies: []
  },
  "b": {
    location: "packages/b",
    workspaceDependencies: [],
    mismatchedWorkspaceDependencies: []    
  }
}

IMO, yarn workspaces list -v --json should output either

1. the same structure when it does in yarn 1 or 2. a valid JSON string, which can be safely JSON.parse(output) at least, even structure diff from yarn 1

[chengcyber]

Thanks for the reply.

For those who run into this issue, try the following util function:

function getWorkspaceInfo() {
  const wsInfoNDJSON = require('child_process').execSync('yarn workspaces list -v --json').toString();
  const wsInfoList = wsInfoNDJSON;
    .split(require('os').EOL)
    .filter(Boolean)
    .map((x) => JSON.parse(x));
  return wsInfoList;
}

[merceyz]

The Project class has all the information about the workspaces, to list workspaces you can look at the code for the workspaces list command https://github.com/yarnpkg/berry/blob/9f8256807f406229333a6f45294ac2d5ca0a941c/packages/plugin-essentials/sources/commands/workspaces/list.ts#L24

If you need help consuming the API I suggest joining the discord channel and asking there